/*
   Mouse Driven Squares Drawing Example Program

   VIZA 652            Fred Parke        11/04/97
*/

#include <stdio.h>	/* define standard I/O routines */
#include <GL/gl.h>	/* define OpenGL graphics routines */
#include <GL/glu.h>	/* define OpenGL utility routines */
#include <glut.h>	/* define GLUT window and device routines */
#include <math.h>	/* define math library routines */

int wh = 500;		/* window dimensions */
int ww = 500;
float size = 10.0;	/* half size of the drawn sqaures	*/

void drawSquare(int x, int y)	/* executed once for each sqaure  */
{
  y = wh-y; 	/* invert y mouse coordinate	*/

  /*  pick a random number for this sqaure 	*/

  glColor3ub((char) random()%256, (char) random()%256, (char) random()%256);

  glBegin(GL_POLYGON);	/*  draw the sqaure	*/
     glVertex2f(x+size, y+size);
     glVertex2f(x-size, y+size);
     glVertex2f(x-size, y-size);
     glVertex2f(x+size, y-size);
  glEnd();
  glFlush();	/* flush out the graphics commands	*/
}

void myinit(void)	/*  intialize window coordiantes	*/
{
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluOrtho2D(0,ww,0,wh);

  glViewport(0,0,ww,wh);
}

void clearwindow(void)	/*  clear the window to black	*/
{
  glClearColor(0,0,0,0);
  glClear(GL_COLOR_BUFFER_BIT);
  glFlush();	/* flush out the graphics commands	*/
}

/*  prodecure to handle mouse events	*/

void mouse(int btn, int state, int x, int y) 
{
  if(btn==GLUT_RIGHT_BUTTON && state==GLUT_DOWN)  exit();
  if(btn==GLUT_MIDDLE_BUTTON && state==GLUT_DOWN) clearwindow();
/*	previous line could be replaced with
  if(btn==GLUT_MIDDLE_BUTTON && state==GLUT_DOWN) glutPostRedisplay();  */
}

/*
   Main program
*/
void main(int argc, char* argv[])
{  
  glutInit(&argc, argv);	/* intialize the glut package	*/

  /* create a single buffer RGB window */

  glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
  glutInitWindowSize(ww,wh);
  glutCreateWindow("Squares");
  
  myinit();	/* Initialize routine */

  glutDisplayFunc(clearwindow); /* register display callback procedure  */
  glutMouseFunc(mouse);		/* register mouse event callback	*/
  glutMotionFunc(drawSquare);	/* register mouse motion callback	*/

  glutMainLoop();	/* enter main loop	*/
}